Letters – by Our Readers


Dear Pat Carson,

I noticed that in your performance numbers of the Beneteau GT41 you use a 20% reserve to calculate range. This is not what the Coast Guard and any boating safety organization will tell you. They will state that you calculate 1/3 for going out, 1/3 for coming home and 1/3 in reserve.

Why would you use 20% which could endanger people who take you seriously? I have been boating for over 60 years and have seen my share of boating mishaps. I am telling you I would not want to run out of gas when the waters turn violent.

For the sake of the boating public, could you please use 1/3 reserve in your future calculations?

You just might save a life.

Will Risseeuw
Redwood City, CA


Thank you for reading the Yachtsman Magazine and for taking the time to write.

Although I appreciate your point of view with regards to a safe fuel reserve, I think that you will find that many, if not most, experienced captains consider a 10% fuel reserve sufficient and many yacht manufacturers use 10 or 15% as a fuel reserve in their range calculations. I use 20% when making my voyage plans to relocate a vessel. Planning a full 33% reserve would be ultra safe. With that being said, there are many other considerations to take into account when planning the safe range of your particular vessel for a particular voyage.

First, consider how you are measuring fuel level. Mechanical fuel gauges are notoriously inaccurate, and will either be very conservative or the tank will be empty when the gauge still shows 1/4 in the tank. I have seen just about every flaw a fuel gauge can have and never trust them. Along the same lines, never trust a boat manufacturer’s published range or fuel capacity numbers. I always check the label on the tank to confirm total and usable capacity and make my voyage plans accordingly. You also want to consider what the sea conditions are, how much gear is on board and whether the bottom is clean or full of barnacles. All of these factors can have a dramatic effect on vessel fuel consumption. And do not forget to take into account fuel consumption of the generator. Although usually in the 1.5 gallon per hour range, that can add up over a 24-hour voyage. To determine a realistic hourly fuel rate, we will also plan a first fuel stop at approximately 1/2 the calculated maximum range. By doing this we can not only confirm the accuracy of the fuel gauges and observe the total fuel consumption rate including the generator, but we can accurately determine the fuel efficiency of the boat based on the condition of the bottom and the weight of persons and gear on board.

On a coastal voyage that is port to port I use 20% reserve for my voyage plan. If the seas and weather are worse than expected I may increase my reserve to 25% or in some cases 30%. If the fuel consumption is higher than expected there is always the option to slow down to displacement speed and shut down the generator to extend the range.

Every skipper must make his or her own voyage plan based on their vessel, the sea and weather conditions, condition of the vessel and their experience. Bottom line: There is no excuse for ever running out of fuel!

Also note that we avoid using the term gas and instead always use the term fuel. I would like to avoid anyone misunderstanding what I want at the fuel dock and gassing up my diesel boat.

Capt. Pat

Hello Jackie,

I saw the mention in the August article. One correction though, my boat is a Yankee One Design, not a Bear Boat.

That’s all, thanks!

Wesley Nunez

Hi Wesley,

Sorry about the description of Flotsam as a Bear Boat. We plastic boat owners know our own, but sometimes miss distinctions in others. To make it up to you, here is a photograph of you on your lovely Yankee One S/V Flotsam.


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